1. Field of the Invention
The present invention relates to a power supply apparatus such as one designed for use in a vehicle to make it run. More particularly, the present invention relates to a power supply apparatus including a voltage detection circuit for a battery.
2. Description of Related Art
A power supply apparatus mounted on a vehicle such as a hybrid car or a fuel battery (fuel cell) powered vehicle includes a voltage detection circuit for detecting the voltage of the battery, in order to enable controlling the battery state based on the detected voltage of the battery. This type of power supply apparatus converts the battery voltage into a digital signal through an A/D converter and, then, supplies the digital signal to a microcomputer mounted on the vehicle. The circuit configuration of this type of power supply apparatus is disclosed, for example, in Japanese Patent Application Laid-Open No. 2001-330653 (hereinafter, referred to as Patent Document 1).
In the vehicular power supply apparatus disclosed in Patent Document 1, a voltage detection circuit for detecting the battery voltage is connected to an A/D converter, and the A/D converter is connected to a microcomputer.
A power supply apparatus mounted on a vehicle employs connectors and lead lines, called wire harnesses, for connections of electronic circuits, in the circuits for detecting the battery voltage and for outputting it to a microcomputer. The lead lines and the connectors in the vehicle are used in hostile external environments such as hostile temperatures and humilities, and are subjected to relatively strong vibrations. Since they are used in hostile environments such as dusty environments, they are prone to faults such as poor connection or brakes. Furthermore, most of portions include lead lines or connectors, which significantly complicates the identification of the portions of faults.